In electrical engineering: the emission of visible light by a p-n
junction across which a forward-biased voltage is applied. In
electrochemistry: emission of light by a molecule which is being
reduced or oxidized on a biased electrode. If the exciting cause
is a photon, rather than an electron, the process is called
photoluminescence.

Electrolyte

A solution through which an electric current may be carried by the
motion of ions.

Electrolyte/Insulator/Silicon (EIS)

Structures at the heart of a broad family of potentiometric
silicon sensors. The best-known member of the family is the
ion-sensitive field effect transistor, known as the ISFET or
CHEMFET and the light-addressable potentiometric sensor LAPS . The
principle of operation of devices using such structures is as
follows. A potential with respect to a reference electrode is
generated at the interface between the liquid solution and the
insulator. The surface potential (ψ0)
is determined by that ionic
species which has the fastest exchange rate (io)
with the membrane
covering the insulator. If no intentional membrane is deposited on
an oxide covered insulator that species will be H+.
Surface
potential changes in turn change the Si flat-band voltage
VFB. The
flat-band voltage is the potential one needs to apply to the Si in
order to have the bands flat throughout the semiconductor. The
flat band voltage of an EIS structure has been shown to be given
by: VFB = EREF - ΦSi/q -
ψ0 - Qins/Cinss where VFB
stands for the flat-band voltage of the structure, EREF for the
reference electrode potential, ΦSi for the work function of
silicon, ψ0
for the surface potential at the insulator/electrolyte
interface, Qins
for the charge at the insulator/silicon interface
and Cins
for the insulator capacitance. At least two terms in the
above equation are not known with a precision greater than a few
hundred millivolts. This is true for EREF
as well as for Qins/Cins
which can vary from device to device by several hundred
millivolts. For a given EIS sensor, these inaccurately known
quantities are constant, and variations in flat-band voltage can
be equated to variations of the surface potential.

Electromotive force (emf) series

A series of chemical elements arranged in order of their
electromotive force. The electromotive force is the greatest
potential difference that can be generated by a particular source
of electric current. In practice this potential may be observable
only when the source is not supplying current, because of its
internal resistance.

Electron

Elementary negative particle whose charge is 1.602
x10-19 coulombs.

Electron state (level)

One of a set of discrete, quantized energies that are allowed for
electrons. In the atomic case each state is specified by 4 quantum
numbers.

Electronegative

Describing elements that tend to gain electrons and form negative
ions. The halogens are typical electronegative elements.